The present disclosure relates to a semiconductor structure, and particularly to a semiconductor structure including a deep isolation trench and a buried plate around a deep capacitor trench and a method of manufacturing the same.
Deep trench capacitors are used in a variety of semiconductor chips for high areal capacitance and low device leakage. Typically, a deep trench capacitor provides a capacitance in the range from 4 fF (femto-Farad) to 120 fF. A deep trench capacitor may be employed as a charge storage unit in a dynamic random access memory (DRAM), which may be provided as a stand-alone semiconductor chip, or may be embedded in a system-on-chip (SoC) semiconductor chip. A deep trench capacitor may also be employed in a variety of circuit applications such as a charge pump or a capacitive analog component in a radio-frequency (RF) circuit.
Deep trench capacitors are formed in a semiconductor substrate, which can be a semiconductor-on-insulator (SOI) substrate or a bulk substrate. Other semiconductor devices such as field effect transistors can be formed on the same semiconductor substrate, thereby enabling embedding of deep trench capacitors into a semiconductor chip. Such embedded deep trench capacitors enable various functionality including embedded dynamic access memory (eDRAM) and other embedded electronic components requiring a capacitor.
Deep trench capacitors can be concurrently formed in conjunction with deep isolation trenches. Deep isolation trenches can be patterned to have a greater width so that the deep isolation trenches extend to a greater depth than the depth of buried plates for deep trench capacitors. However, downward and lateral dopant diffusion from the buried plates of deep trench capacitors into an underlying semiconductor substrate can provide a leakage current path around the bottom surface of deep isolation trenches. To counter the effect of such vertical dopant diffusion from buried plates, the depth differential between the depth of deep isolation trenches and the depth of deep trenches for deep trench capacitors need to be increased. Such an increase in the depth differential requires wider deep isolation trenches, i.e., a greater width for deep trench moat structures filling the deep isolation trenches, and accompanying increase in the areal footprint for the deep isolation trenches.